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Post Info TOPIC: Spot an L99 4.3 Liter Baby LT1 before its too late!


$y$Op

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Spot an L99 4.3 Liter Baby LT1 before its too late!


As the years go by more and more we are finding people whom come to realize their 5.7 liter LT1's are really 4.3 liter L99's.

This sort of thing has been going on forever, since way back in the day when the 350 had a baby brother 305.

Its very easy to spot an L99 from an LT1, to do this you need only look at the back of the engine on the top drivers side. There should be markings that clearly say GM 5.7 cast into the block.

The L99 engine looks to the un-trained eye almost identical to that of the LT1. The primary diffrence being in displacement. The LT1 displaces 5.7 liters, while the L99 displaces only 4.3! The L99 was found in vehicles such as the 1993-1996 Caprice, Impalla and other V8 GM vehicles.

We didnt want to have to tear down an L99 however for the benifit of research and to futher test the theory of possible advantages in some areas such as heads and intake we will undertake this endevor and keep you posted.

If you have any information or photos please feel free to add to this thread.

-- Edited by Administrator at 19:29, 2008-04-09

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$y$Op

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One more sure fire way to tell if you have a 350 is to remove the cylinder heads and measure the bore. All 350's will have at least a 4.00 inch bore.

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User

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Put the L99 crank in an LT1 block and build a 302 LT1.

302 with a roller cam.

9,000RPM street pounder.

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We do PRECISION GUESSWORK based on vague assumptions and unreliable data of dubious accuracy provided by persons of questionable intellectual capacity. Now what can we fix for you today?


OUT-OF-HAND

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Part number for LT1 Block - 10125327

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State of Michigan Certified Master Auto Mechanic +2

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Anonymous

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can you use the 350lt1 crank and rods in the baby lt1 with out any issues to gain more power

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OUT-OF-HAND

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I am under the impression the difference between the two is bore size. The LT1 350 will have a 4 inch bore, where as the other one will have a much smaller piston size. However I am basing this assumption on the older 5.7's and 5.0's of the TPI era. 

I am uncertain if the crank and rods are different, as I have not done much with the smaller engine and have rejected all of them prior to purchase. Sorry I could not be of more help, if you do happen to research the rod and cranks please post up your findings.

I noticed that Hillbilly claims you can put the L99 crank in the LT1 however I myself have never done this and don't understand why anyone would want to lower the cubic inches.



-- Edited by SELLC on Saturday 25th of December 2010 07:01:56 PM

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State of Michigan Certified Master Auto Mechanic +2

Specialty Certified Since 1994

Anonymous

Date:

the rods are 5.94 with a 3in stroke and the pistons are the same as the vortec 305 im not sure on the crank jounal thickness since in the older engines they were thinner

and yeah if the crank is the same thikness you could make a lt1 302

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